Purpose: As an alternative to single-cycle cyclophosphamide, thiotepa, and carboplatin (CTCb) intensification, we evaluated the feasibility of administering one-quarter dose CTCb for four cycles with peripheral-blood progenitor-cell (PBPC) and filgrastim (granulocyte colony-stimulating factor [G-CSF]) in advanced-stage breast cancer patients.
Patients and methods: From June 1992 to August 1993, 20 stage IIIB (n = 7) and IV (n = 13) breast cancer patients received 78 cycles of induction with doxorubicin 90 mg/m2 by intravenous (IV) bolus with G-CSF 5 microg/kg/d by subcutaneous injection (SC) repeated every 14 to 21 days for four cycles. PBPC were collected by 2-hour single-blood volume leukapheresis on 2 consecutive days at the time of hematologic recovery from each cycle of doxorubicin. Eighteen patients received 61 cycles of intensification with cyclophosphamide 1,500 mg/m2, thiotepa 125 mg/m2, and carboplatin 200 mg/m2 by IV continuous infusion with G-CSF 10 microg/kg/d SC and PBPC support repeated every 21 to 42 days for four cycles.
Results: Twelve of 20 patients (60%) completed all four planned cycles of doxorubicin induction followed by four cycles of one-quarter dose CTCb intensification. Statistically significantly decreases in the yield of mononuclear cells (MNC) (median slope per day, -0.032; P = .03), granulocyte-macrophage colony-forming unit (CFU-GM) (median slope per day, -0.57; P = .0008), and burst-forming unit-erythroid (BFU-E) (median slope per day, -1.18; P = .006) were observed over the course of the eight leukaphereses. Of 18 patients who began CTCb, 12 (67%) completed four cycles. Six patients were removed from study during intensification: two for progressive disease (PD), one refused further treatment, and three for dose-limiting hematologic toxicity. A fourth patient fulfilled the criteria for dose-limiting hematologic toxicity after cycle 4. The toxicity of the multiple cycle CTCb intensification regimen consisted of grade IV leukopenia, grade IV thrombocytopenia, and febrile neutropenia in 100%, 100%, and 26% of cycles, respectively. The median duration of each CTCb cycle was 24 days (range, 18 to 63), and the median duration of an absolute neutrophil count (ANC) < or = 500/microL and platelet count < or = 20,000/microL during each cycle was 6 days (range, 2 to 15) and 4 days (range, 0 to 38), respectively.
Conclusion: It is feasible to administer repetitive cycles of one-quarter dose CTCb intensification with PBPC and G-CSF. Additional studies are required to determine whether multiple cycles of CTCb intensification might offer a therapeutic advantage over a single high-dose cycle.